U.S. patent application number 12/912434 was filed with the patent office on 2011-05-05 for light-emitting device, method of manufacturing light-emitting device, and illumination device.
This patent application is currently assigned to TOSHIBA LIGHTING & TECHNOLOGY CORPORATION. Invention is credited to Nobuhiko Betsuda, Kiyoshi Nishimura, Kozo Ogawa, Soichi Shibusawa.
Application Number | 20110101384 12/912434 |
Document ID | / |
Family ID | 43514091 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110101384 |
Kind Code |
A1 |
Betsuda; Nobuhiko ; et
al. |
May 5, 2011 |
LIGHT-EMITTING DEVICE, METHOD OF MANUFACTURING LIGHT-EMITTING
DEVICE, AND ILLUMINATION DEVICE
Abstract
According to one embodiment, a light-emitting device includes a
substrate, a plurality of pads and a plurality of light-emitting
elements. The pads has electric conductance, and are arranged on
the substrate. A reflecting layer which is formed by electroplating
is provided on a surface of each of the pads. The light-emitting
elements are mounted on the pads. A depressed part is left on the
substrate. The depressed part is formed on the substrate by
removing a pattern on the substrate, by which the pads are
electrically connected.
Inventors: |
Betsuda; Nobuhiko;
(Yokosuka-Shi, JP) ; Ogawa; Kozo; (Yokosuka-Shi,
JP) ; Nishimura; Kiyoshi; (Yokosuka-Shi, JP) ;
Shibusawa; Soichi; (Yokosuka-Shi, JP) |
Assignee: |
TOSHIBA LIGHTING & TECHNOLOGY
CORPORATION
YOKOSUKA-SHI
JP
|
Family ID: |
43514091 |
Appl. No.: |
12/912434 |
Filed: |
October 26, 2010 |
Current U.S.
Class: |
257/88 ;
257/E21.506; 257/E33.066; 438/29 |
Current CPC
Class: |
H01L 33/62 20130101;
H01L 2224/48091 20130101; H01L 2224/48091 20130101; H05K 2201/2054
20130101; H01L 33/56 20130101; H01L 2933/0066 20130101; H05K 3/242
20130101; H05K 2201/10106 20130101; H01L 2224/45144 20130101; H01L
25/0753 20130101; H01L 2224/45144 20130101; H01L 2924/00 20130101;
H01L 2924/00 20130101; H05K 2201/09036 20130101; H05K 2203/175
20130101; H01L 33/60 20130101; H01L 2224/73265 20130101; H01L
2224/48091 20130101; H01L 2924/00014 20130101 |
Class at
Publication: |
257/88 ; 438/29;
257/E33.066; 257/E21.506 |
International
Class: |
H01L 33/08 20100101
H01L033/08; H01L 21/60 20060101 H01L021/60 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2009 |
JP |
2009-249934 |
Feb 12, 2010 |
JP |
2010-029541 |
Oct 15, 2010 |
JP |
2010-232291 |
Claims
1. A light-emitting device comprising: a substrate; a plurality of
pads arranged on the substrate, each of the pads having electric
conductance and a surface on which a reflecting layer formed by
electroplating is provided; a plurality of light-emitting elements
which are mounted on the pads; and a depressed part which is left
on the substrate, the depressed part being formed on the substrate
by removing a pattern on the substrate, by which the pads are
electrically connected.
2. The light-emitting device of claim 1, further comprising: a
conductor pattern which supplies an electric current to the
light-emitting elements, the conductor pattern including the pads
and being formed on the substrate.
3. The light-emitting device of claim 1, wherein the depressed part
extends along an edge of the substrate in a position distant from
the edge of the substrate.
4. The light-emitting device of claim 3, wherein the substrate
includes a piercing part through which a fixing tool is inserted,
the piercing part is positioned between the edge of the substrate
and the depressed part, and the depressed part includes a part
which detours around the piercing part in a position corresponding
to the piercing part.
5. The light-emitting device of claim 1, wherein the substrate has
electric insulating property, and the depressed part has a
bottom.
6. The light-emitting device of claim 1, wherein the pattern
includes a plurality of connection lines which are guided from the
pads to a plurality of positions on the substrate, the depressed
part includes a plurality of cutoff parts formed in the positions
to which the connection lines are guided, and the cutoff parts are
opened to an edge of the substrate and distant from one
another.
7. The light-emitting device of claim 6, wherein the substrate
includes a first surface on which the pads and the connection lines
are arranged, a second surface which is positioned on a side
opposite to the first surface, and an outer peripheral surface
which connects the first surface with the second surface, and each
of the cutoff parts is opened to a corner part of the substrate
which is defined by the first surface and the outer peripheral
surface, and has a bottom which connects to the outer peripheral
surface.
8. The light-emitting device of claim 6, wherein a conductor is
deposited on the second surface of the substrate.
9. A method of manufacturing a light-emitting device, comprising:
forming a plurality of pads which have electric conductance, and a
pattern which electrically connects the pads, on a substrate;
forming a reflecting layer on surfaces of the pads subjecting the
pads to electroplating; removing the pattern from the substrate
after the reflecting layer is formed on the pads; and mounting a
plurality of light-emitting elements on the pads.
10. The method of claim 9, wherein a depressed part is formed on
the substrate when the pattern is removed from the substrate.
11. An illumination device comprising: a main body; and a
light-emitting device supported by the main body, the
light-emitting device including: a substrate; a plurality of pads
arranged on the substrate, each of the pads having electric
conductance and a surface on which a reflecting layer formed by
electroplating is provided; a plurality of light-emitting elements
which are mounted on the pads; and a depressed part which is left
on the substrate, the depressed part being formed on the substrate
by removing a pattern on the substrate, by which the pads are
electrically connected.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Applications No. 2009-249934, filed
Oct. 30, 2009; No. 2010-029541, filed Feb. 12, 2010; and No.
2010-232291, filed Oct. 15, 2010; the entire contents of all of
which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a
light-emitting device using a light-emitting element such as a
light-emitting diode, a method of manufacturing the light-emitting
device, and an illumination device to which the light-emitting
device is mounted.
BACKGROUND
[0003] In recent years, illumination devices using a plurality of
light-emitting diodes as light source have been put into practical
use. The illumination devices of this type are used as, for
example, surface-mounted general lighting which is directly mounted
on the indoor ceiling. For example, a conventional illumination
device disclosed in Jpn. Pat. Appln. KOKAI Pub. No. 2009-54989
comprises a base member, and a plurality of light-emitting devices
mounted on the base member. Each light-emitting device has a
substrate formed of ceramics, and a plurality of light-emitting
diodes. The light-emitting diodes are fixed to the substrate with
adhesive made of epoxy resin.
[0004] On the other hand, in light-emitting devices using
light-emitting diodes as light source, it is desired to efficiently
take light emitted by the light-emitting diodes out of the
light-emitting device. To satisfy the demand, known is a
conventional light-emitting device having a structure in which a
plurality of pads, on which light-emitting diodes are mounted, are
provided on the substrate, and surfaces of the pads are covered
with a light-reflecting layer. The light-reflecting layer is formed
on the surfaces of the pads by subjecting the pads to
electroplating.
[0005] Electroplating has advantages of good close contact of metal
coating with product to be treated, and inexpensive manufacturing
cost. In the light-emitting device, however, since a plurality of
pads are arranged at intervals on the substrate, when the pads are
subjected to electroplating, it is necessary to electrically
connect the pads by a dedicated conductor pattern, and maintain all
the pads at the same potential.
[0006] In addition, the conductor pattern becomes redundant after
electroplating is finished. Therefore, it is necessary to perform
work in which the conductor pattern is removed from the substrate
by boring a number of holes in the substrate along the conductor
pattern, and electrical connection between the pads by the
conductor pattern is severed. The work of boring holes in the
substrate has a large number of steps, and requires much time and
labor. This decreases productivity and increases the cost of
producing the light-emitting device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a plan view of a light-emitting device according
to a first embodiment;
[0008] FIG. 2 is a cross-sectional view taken along line F2-F2 of
FIG. 1;
[0009] FIG. 3 is a plan view of a substrate which has a first
conductor pattern including a plurality of pads, and a second
conductor pattern, in the first embodiment;
[0010] FIG. 4 is a cross-sectional view taken along line F4-F4 of
FIG. 3;
[0011] FIG. 5 is a plan view of the substrate in a state where a
common line of the second conductor pattern is removed, in the
first embodiment;
[0012] FIG. 6 is a cross-sectional view taken along line F6-F6 of
FIG. 5;
[0013] FIG. 7 is a plan view of the substrate in a state where
light-emitting elements are mounted on the pads of the first
conductor pattern and the light-emitting elements are covered with
a sealing member, in the first embodiment;
[0014] FIG. 8 is a cross-sectional view of the light-emitting
device, illustrating a state where a protective cover is separated
from the substrate, in the first embodiment;
[0015] FIG. 9 is a side view of an illumination device in which a
pair of the light-emitting devices is fixed to a base, in the first
embodiment;
[0016] FIG. 10 is a plan view of the illumination device according
to the first embodiment;
[0017] FIG. 11 is a perspective view of an illumination device
according to a second embodiment;
[0018] FIG. 12 is a plan view of a light-emitting device according
to a third embodiment;
[0019] FIG. 13 is a plan view of a substrate which has a first
conductor pattern including a plurality of pads, and a second
conductor pattern, in the third embodiment;
[0020] FIG. 14 is a plan view of the substrate, illustrating a
state where a common line of the second conductor pattern is
removed and a plurality of light-emitting elements are mounted on
the pads, in the third embodiment;
[0021] FIG. 15 is a plan view of the substrate, illustrating a
state where the common line of the second conductor pattern is
removed and a sealing member is applied onto the pads on which the
light-emitting elements are mounted, in the third embodiment;
[0022] FIG. 16 is a plan view of the substrate, to which a
thermally radiative sheet is affixed, in the third embodiment;
[0023] FIG. 17 is a cross-sectional view taken along line F17-F17
of FIG. 12;
[0024] FIG. 18 is a circuit diagram, illustrating a state where the
light-emitting elements are electrically connected, in the third
embodiment;
[0025] FIG. 19 is a plan view of a light-emitting device according
to a fourth embodiment;
[0026] FIG. 20 is a plan view of a substrate used for a
light-emitting device of a fifth embodiment;
[0027] FIG. 21 is a plan view of the substrate, illustrating a
state where electrical connection of pads is severed by a second
conductor pattern, in the fifth embodiment;
[0028] FIG. 22 is a plan view of the substrate, illustrating a part
F22 of FIG. 20 in an enlarged state;
[0029] FIG. 23 is a plan view of the substrate, illustrating a part
F23 of FIG. 21 in an enlarged state; and
[0030] FIG. 24 is a cross-sectional view taken along line F24-F24
of FIG. 23.
DETAILED DESCRIPTION
[0031] In general, according to one embodiment, a light-emitting
device comprises a substrate, a plurality of pads, and a plurality
of light-emitting elements. The pads have conductivity, and are
arranged on the substrate. A reflecting layer formed by
electroplating is provided on surfaces of the pads. The
light-emitting elements are mounted on the respective pads. A
depressed part remains on the substrate. The depressed part is
formed in the substrate by removing a pattern on the substrate,
which is electrically connected with the pads.
[0032] The substrate is preferably formed of material which has
thermal conductivity lower than that of metal. However, it is
possible to use a substrate having a core material formed of metal
which has excellent thermal conductivity such as aluminum. In
addition, although the pads are preferably used as wiring pattern
which supplies electric current to the light-emitting elements, the
pads are not limited to being used as wiring pattern. Specifically,
there are cases where it is sufficient that the pads have a
function of reflecting light emitted by the light-emitting devices,
or a function as heat spreader which spreads heat generated by the
light-emitting elements.
[0033] As the light-emitting elements, it is possible to use
semiconductor light-emitting elements such as light-emitting diode
chips. The light-emitting elements can be mounted on the substrate
by, for example, the chip-on-board method or surface mount method.
However, the method of mounting the light-emitting elements on the
substrate is not specifically limited. In addition, the specific
number of light-emitting elements and pads is not specifically
limited.
[0034] The pattern which is removed from the substrate is used for
maintaining all the pads at the same potential when the pads are
subjected to electroplating. In addition, the depressed part is a
mark left on the substrate after the pattern is removed from the
substrate, and the shape and the size of the depressed part are not
specifically limited.
First Embodiment
[0035] A first embodiment will be described hereinafter with
reference to FIG. 1 to FIG. 10.
[0036] FIG. 1 to FIG. 8 illustrate a light-emitting device 1 which
serves as illumination light source. As illustrated in FIG. 1 and
FIG. 2, the light-emitting device 1 comprises a substrate 2, a
plurality of light-emitting elements 3, a plurality of sealing
members 4, and a protective cover 5.
[0037] The substrate 2 is formed of synthetic resin material, such
as glass epoxy resin, which has thermal conductivity lower than
that of metal. The material of the substrate 2 is not limited to
glass epoxy resin, by other synthetic resin materials or ceramics
materials can be used for the substrate 2. Although the substrate 2
is preferably formed of material which has thermal conductivity
lower than that of metal, it is possible to adopt a substrate which
has a core material formed of metal having excellent thermal
conductivity such as aluminum.
[0038] As illustrated in FIG. 1 and FIG. 2, the substrate 2 has an
elongated shape which has a pair of long sides 2a and 2b, and a
pair of short sides 2c and 2d. In addition, the substrate 2 has a
first surface 6a, and a second surface 6b positioned opposite to
the first surface 6a. The first and the second surfaces 6a and 6b
are flat surfaces.
[0039] As illustrated in FIGS. 3 and 4, a first conductor pattern 7
and a second conductor pattern 8 are formed on the first surface 6a
of the substrate 2. The first conductor pattern 7 have a plurality
of pads 9 and an power supply conductor 10. Each pad 9 has an
almost pentagonal shape in which one end is pointed. In the first
embodiment, the pads 9 are arranged in 12 columns at intervals in
the longitudinal direction of the substrate 2, and arranged in 4
rows at intervals in a direction perpendicular to the longitudinal
direction of the substrate 2.
[0040] Therefore, forty-eight pads 9 are regularly arranged in rows
and columns on the first surface 6a of the substrate 2. In other
words, the forty-eight pads 9 form twelve pad columns 13 which are
arranged at intervals in the longitudinal direction of the
substrate 2. Each pad column 13 has four pads 9 arranged in the
direction perpendicular to the longitudinal direction of the
substrate 2.
[0041] In addition, the pad columns 13 are divided into six pad
columns 13 which are positioned on the right side of a center line
O1, which runs through the center of the longitudinal direction of
the substrate 2, and six pad columns 13 which are positioned on the
left side of the center line O1. The pad columns 13 positioned on
the right side of the center line O1 and the pad columns 13
positioned on the left side of the center line O1 are arranged
symmetrically with respect to the center line O1.
[0042] As illustrated in FIG. 3, in each pad column 13, each of
three pads 9 other than one pad 9 adjacent to the long side 2a of
the substrate 2 has a wire connecting part 14. Each wire connecting
part 14 has a straight-line shape, and extends from an edge of the
pad 9 in the direction perpendicular to the longitudinal direction
of the substrate 2. A distal end of the wire connecting part 14 is
positioned directly before the adjacent pad 9.
[0043] The power supply conductor 10 includes a plurality of first
power supply patterns 15, a second power supply pattern 16 which
has a cathode terminal 11a and a third power supply pattern 17
which has an anode terminal 11b. Each of the first power supply
patterns 15 is arranged between adjacent pad columns 13. The second
power supply pattern 16 extends along the long side 2b of the
substrate 2, in the center part of the substrate 2 along the
longitudinal direction of the substrate 2. The third power supply
pattern 17 extends over the whole length of the substrate 2 to run
along the long side 2a of the substrate 2, and connects two pad
columns 13 which are arranged at both ends of the longitudinal
direction of the substrate 2. The cathode terminal 11a and the
anode terminal 11b are positioned on the center line O1 of the
substrate 2. The cathode terminal 11a and the anode terminal 11b
are electrically connected to a power supply circuit through lead
lines.
[0044] As illustrated in FIG. 2, the first conductor pattern 7
including the pads 9 has a three-layer structure including a copper
layer 20, a nickel plating layer 21, and a silver plating layer 22.
The copper layer 20 is formed by etching a copper foil deposited on
the first surface 6a of the substrate 2. The nickel plating layer
21 is formed on the copper layer 20, by subjecting the copper layer
20 to electroplating. The silver plating layer 22 is formed on the
nickel plating layer 21, by subjecting the nickel plating layer 21
to electroplating. The silver plating layer 22 covers the nickel
plating layer 21, and forms a reflecting layer exposed on the
surface of the first conductor pattern 7. Therefore, the surface of
the first conductor pattern 7 is a light-reflecting surface. The
total light reflectance of the light-reflecting surface is, for
example, 90%.
[0045] The second conductor pattern 8 is used for maintaining all
the pads 9 at the same potential, when the pads 9 of the first
conductor pattern 7 are subjected to electroplating. Specifically,
the second conductor pattern 8 has a common line 24 and a plurality
of branch lines 25. The common line 24 extends in a straight line
over the whole length of the substrate 2 to run along the long side
2b of the substrate 2. In addition, the common line 24 is distant
from an end edge of the substrate 2, which defines the long side 2b
of the substrate 2, by a predetermined distance D. Although the
common line 24 is preferably formed in a straight-line shape, but
may be formed in, for example, an arc shape or a meandering
shape.
[0046] The branch lines 25 are branched from the common line 24,
and extend in a straight line toward spaces between adjacent pad
columns 13. Distal ends of the branch lines 25 are connected to the
respective pads 9 of the pad columns 13. Therefore, all the pads 9
are electrically connected to the common line 24 through the branch
lines 25.
[0047] The second conductor pattern 8 is formed on the first
surface 6a of the substrate 2 simultaneously with the first
conductor pattern 7, and has a three-layer structure similar to
that of the first conductor pattern 7. Specifically, as illustrated
in FIG. 4, the second conductor pattern 8 includes the copper layer
20, the nickel plating layer 21, and the silver plating layer 22.
The silver plating layer 22 is exposed on the surface of the second
conductor pattern 8. Therefore, the surface of the second conductor
pattern 8 is also a light-reflecting surface.
[0048] In the first embodiment, light-emitting diode chips are used
as the light-emitting elements 3. The light-emitting diode chips
are, for example, InGaN-based elements, and includes sapphire board
which has light transmittance, and a light-emitting layer which is
deposited on the sapphire board and emits blue light. The
light-emitting layer is formed by depositing an N-type nitride
semiconductor layer, an InGaN light-emitting layer, and a P-type
nitride semiconductor layer each other.
[0049] In addition, each of the light-emitting diode chips includes
a positive electrode and a negative electrode, which supply
electric current to the light-emitting layer. The positive
electrode has a P-type electrode pad which is formed on the P-type
nitride semiconductor layer. The negative electrode has an N-type
electrode pad which is formed on the N-type nitride semiconductor
layer.
[0050] The light-emitting elements 3 are individually mounted on
the silver plating layer 22 serving as the surfaces of the
respective pads 9, by using an adhesive 26 formed of silicone
resin. Therefore, in the first embodiment, forty-eight
light-emitting elements 3 are regularly arranged in rows and
columns on the first surface 6a of the substrate 2. The
light-emitting elements 3 are smaller in shape than the pads 9.
Therefore, the light-reflecting pads 9 project around the
light-emitting elements 3 on the first surface 6a of the substrate
2.
[0051] As illustrated in FIG. 2, the positive electrode of each
light-emitting element 3 is electrically connected to the pad 9, to
which the light-emitting element 3 is affixed, through a bonding
wire 28. The negative electrode of each light-emitting element 3 is
electrically connected to the wire connecting part 14 of the
adjacent pad 9, through another bonding wire 29.
[0052] As illustrated in FIG. 7, in each of the two pad columns 13
which are adjacent to each other with the center line O1 of the
substrate 2 interposed therebetween, the negative electrode of the
light-emitting element 3 which is affixed to the pad 9 adjacent to
the long side 2b of the substrate 2 is electrically connected to
the second power supply pattern 16 through the bonding wire 29.
[0053] In each of the other pad columns 13, the negative electrode
of the light-emitting element 3 which is affixed to the pad 9
adjacent to the long side 2b of the substrate 2 is electrically
connected to the first power supply pattern 15 through the bonding
wire 29.
[0054] As a result, the light-emitting elements 3 are connected in
series in each pad column 13, and form twelve light-emitting
element columns which correspond to the pad columns. The twelve
light-emitting element columns are connected in parallel with the
second power supply pattern 16 and the third power supply pattern
17.
[0055] In the first embodiment, gold wires are used as the bonding
wires 28 and 29. In addition, the bonding wires 28 and 29 are
connected to the positive electrodes and the negative electrodes of
the light-emitting elements 3 through bumps mainly formed of gold
(Au), to improve the mounting strength of the bonding wires 28 and
29 and reduce damage to the light-emitting elements 3.
[0056] The second conductor pattern 8, which maintains all the pads
9 of the first conductor pattern 7 at the same potential, is
redundant after the pads 9 are subjected to electroplating.
Therefore, in the first embodiment, after the pads 9 are subjected
to electroplating, the common line 24 of the second conductor
pattern 8 is removed, to sever electrical connection between the
pads 9 by the second conductor pattern 8.
[0057] As a result, as illustrated in FIG. 5 to FIG. 7, a
groove-like depressed part 33 is formed in the first surface 6a.
The depressed part 33 is a trace which is left after the common
line 24 is removed, and extends in a straight line along the long
side 2b of the substrate 2. The depressed part 33 is positioned
between the end edge of the substrate 2 which defines the long side
2b of the substrate 2 and the first power supply patterns 15 on the
substrate 2, and is distant from the end edge of the substrate 2 by
the predetermined distance. The depressed part 33 is defined by a
bottom surface 33a and a pair of side surfaces 33b and 33c, and
opened to the first surface 6a of the substrate 2. In FIG. 1, FIG.
5 and FIG. 7, the depressed part 33 is painted with black color to
clearly distinguish the depressed part 33 from the second conductor
pattern 8.
[0058] By presence of the depressed part 33, only the branch lines
25 of the second conductor pattern 8 are left on the first surface
6a of the substrate 2. In addition, a creepage distance between the
end edge of the substrate 2 which defines the long side 2b of the
substrate 2 and the first power supply patterns 15 on the substrate
2 is a value obtained by adding the height of the side surfaces 33b
and 33c of the depressed part 33. Therefore, the creepage distance
is longer than the clearance between the end edge of the substrate
2 and the first conductor pattern 7 by the depth of the depressed
part 33.
[0059] The shape of the depressed part 33 is not limited to the
first embodiment. For example, the depressed part 33 may have a
V-shaped or U-shaped cross section in the direction perpendicular
to the longitudinal direction of the substrate 2.
[0060] The sealing members 4 are elements for sealing the
individual light-emitting elements 3 and the bonding wires 28 and
29 connected to the light-emitting elements 3 on the pads 9, and
rise in a hemispherical shape from the respective pads 9. For
example, transparent silicone resin having light transmittance is
used as the sealing members 4. The silicone resin is applied in a
liquid state onto each pad 9. The applied silicone resin is cured
by heating or natural drying, and held on each pad 9.
[0061] The sealing member 4 contains fluorescent material. The
fluorescent material is uniformly dispersed in the sealing members
4. As the fluorescent material, used is yellow fluorescent material
which is excited by blue light emitted by the light-emitting
elements 3 and emits yellow light. The fluorescent material mixed
into the sealing members 4 is not limited to yellow fluorescent
material. For example, to improve the color rendering properties of
light emitted by the light-emitting elements 3, it is possible to
add red fluorescent material which is excited by blue light and
emits red light, or green fluorescent material which emits green
light, to the sealing members 4.
[0062] As illustrated in FIG. 2, the protective cover 5 covers the
substrate 2 on which the light-emitting elements 3 are sealed. The
protective cover 5 is formed of synthetic resin material having
light transmittance, such as transparent acrylic resin and
polycarbonate resin. The protective cover 5 includes a receptacle
35 into which the substrate 2 is fitted. The receptacle 35 has a
bottom surface 35a which is opposed to the first surface 6a of the
substrate 2, and an opening end 35b which is opposed to the bottom
surface 35a. The opening end 35b of the receptacle 35 is opened to
a back surface 5a of the protective cover 5.
[0063] A plurality of depressions 36 are formed in the bottom
surface 35a of the receptacle 35. The depressions 36 are arranged
in rows and columns on the bottom surface 35a to correspond to the
respective light-emitting elements 3. The depressions 36 have a
conic shape which has a circular opening part opened to the bottom
surface 35a, and are opposed to the respective sealing members 4
covering the light-emitting elements 3. The spherical top parts of
the sealing members 4 get into the respective depressions 36
through the opening parts of the depressions 36.
[0064] In addition, the protective cover 5 has a flange part 37.
The flange part 37 surrounds the opening end 35b of the receptacle
35, and projects from the outer peripheral surface of the
protective cover 5 to the outside of the protective cover 5.
[0065] As illustrated in FIG. 2, the substrate 2 is fixed within
the receptacle 35 of the protective cover 5, by transparent
silicone-resin-based adhesive 38. The adhesive 38 is filled into a
space between the first surface 6a of the substrate 2 and the
bottom surface 35a of the receptacle 35. In the state where the
substrate 2 is fixed within the receptacle 35 of the protective
cover 5, the opening parts of the depressions 36 are closed with
the sealing members 4 and the adhesive 38. As a result, the inside
parts of the depressions 36 become closed spaces, and an air layer
39 is formed between the protective cover 5 and the sealing members
4. In addition, in the state where the substrate 2 is fixed within
the receptacle 35 of the protective cover 5, the second surface 6b
of the substrate 2 is positioned inside the receptacle 35 more than
the back surface 5a of the protective cover 5 does.
[0066] Next, a process of manufacturing the light-emitting device 1
is explained with reference to FIG. 3 to FIG. 8.
[0067] First, the first conductor pattern 7 and the second
conductor pattern 8 are formed on the first surface 6a of the
substrate 2. Specifically, the foil deposited on the first surface
6a is etched, and thereby a copper layer 20 of the first conductor
pattern 7 and a copper layer 20 of the second conductor pattern 8
are formed. Among the copper layer 20 of the first conductor
pattern 7, parts which form the pads 9 are electrically connected
to each other through the copper layer 20 of the second conductor
pattern 8. Therefore, all the parts of the copper layer 20 of the
first conductor pattern 7, which form the pads 9, are maintained at
the same potential.
[0068] In this state, the copper layers 20 of the first and the
second conductor patterns 7 and 8 are subjected to electroplating,
and thereby a nickel plating layer 21 is formed on the copper
layers. Thereafter, the nickel plating layer 21 is subjected to
electroplating, and thereby a silver plating layer 22 is formed on
the nickel plating layer 21. In the step of performing
electroplating, all the parts which form the pads 9 in the copper
layer 20 of the first conductor pattern 7 are maintained at the
same potential. Therefore, the nickel plating layer 21 and the
silver plating layer 22 are formed on the copper layer 20 of the
first conductor pattern 7, by using the copper layer 20 of the
first conductor pattern 7 as cathode, using the same metal as
plating layer as anode, and causing an electric current to flow
between the cathode and the anode. The nickel plating layer 21 and
the silver plating layer 22 are also formed on the copper layer 20
of the second conductor pattern 8 simultaneously with the first
conductor pattern 7.
[0069] Thereafter, as illustrated in FIG. 5 and FIG. 6, the common
line 24 of the second conductor pattern 8 is removed from the first
surface 6a of the substrate 2. Specifically, the common line 24 on
the first surface 6a is scraped away by using an electrical tool
such as a router and a trimmer. As a result, electrical connection
between the pads 9 of the first conductor pattern 7 and the common
line 24 is severed, and the pads 9 become electrically
independent.
[0070] Simultaneously with scraping away the common line 24 from
the first surface 6a, a groove-like depressed part 33 is formed in
the first surface 6a. The depressed part 33 crosses over the bases
of the branch lines 25 branching off from the common line 24. As a
result, the branch lines 25 are left on the first surface 6a of the
substrate 2, in a state of being electrically separated from each
other.
[0071] Thereafter, light-emitting elements 3 are affixed on the
respective pads 9 of the first conductor pattern 7. Then, the
positive electrode of each light-emitting element 3 is electrically
connected to the pad 9, to which the light-emitting element 3 is
affixed, by bonding wire 28. In the same manner, the negative
electrode of each light-emitting element 3 is connected to the wire
connecting part 14 of the adjacent pad 9 and the first power supply
pattern 15 by bonding wire 29.
[0072] Then, sealing members 4 are individually applied onto the
respective pads 9 to which the light-emitting elements 3 are
affixed, to cover the light-emitting elements 3 and the bonding
wires 28 and 29 connected to the light-emitting elements 3 with the
sealing members 4. Thereafter, the applied sealing members 4 are
cured. Thereby, the light-emitting elements 3 and the bonding wires
28 and 29 are sealed on the first surface 6a of the substrate 2 by
the sealing members 4.
[0073] Next, as illustrated in FIG. 8, the protective cover 5 is
held in a position in which the bottom surface 33a of the
receptacle 35 of the protective cover 5 faces upward. In this
state, silicone-based, adhesive 38 is applied to the bottom surface
33a of the receptacle 35. Then, the substrate 2 on which the
light-emitting elements 3 are sealed is deposited in the receptacle
35 of the protective cover 5, and the hemispherical sealing members
4 covering the light-emitting elements 3 are positioned in the
opening parts of the depressions 36.
[0074] As a result, the first surface 6a of the substrate 2 is
affixed to the bottom surface 35a of the receptacle 35 by the
silicone-based adhesive 38, and the substrate 2 is united with the
protective cover 5. Thereby, a series of manufacturing steps of the
light-emitting device 1 is finished.
[0075] Next, an illumination device 41 which uses the
light-emitting device 1 as light source will be explained
hereinafter, with reference to FIGS. 9 and 10 in addition to the
above drawings. The illumination device 41 is used by directly
attaching the illumination device 41 to, for example, the indoor
ceiling C. The illumination device 41 comprises a base 42, and two
light-emitting devices 1. The base 42 is an example of a main body
of the illumination device 41, and formed in a rectangular shape by
using metal material such as aluminum. The base 42 is fixed to the
ceiling C by bolts.
[0076] The two light-emitting devices 1 are arranged in a straight
line along a longitudinal direction of the base 42, and are
electrically connected to a power supply unit (not shown) including
a power supply circuit. Each light-emitting device 1 is fixed to
the base 2 by a plurality of screws 43. The screws 43 are screwed
into the base 2 through the flange part 37 of the protective cover
5. Therefore, the protective cover 5 also functions as bracket to
fix the light-emitting devices 1 to the base 42.
[0077] In a state where the light-emitting devices 1 are fixed to
the base 42, the back surface 5a of the protective cover 5 contacts
the base 42, and the opening end 35b of the receptacle 35 is closed
by the base 42. The second surface 6b of the substrate 2, which is
received into the receptacle 35 goes inside the receptacle 35 more
than the back surface 5a of the protective cover 5 does, as
illustrated in FIG. 2. Therefore, the second surface 6b of the
substrate 2 is distant from the base 42. A space between the
substrate 2 and the base 42 functions as a thermal insulating layer
44. The thermal insulating layer 44 is not limited to the space.
For example, a thermal insulating material may be filled into the
space between the substrate 2 and the base 42.
[0078] In the illumination device 41 having the above structure, a
voltage is applied to the two light-emitting devices 1 through the
power supply unit. As a result, the light-emitting elements 3 on
the substrate 2 emit light all together. The blue light emitted by
the light-emitting elements 3 is made incident on the sealing
members 4. Part of the blue light made incident on the sealing
members 4 is absorbed into the yellow fluorescent material. The
rest of the blue light passes through the sealing members 4,
without being absorbed into the yellow fluorescent material.
[0079] The yellow fluorescent material which has absorbed the blue
light is excited and emits yellow light. Since yellow light passes
through the sealing members 4, the yellow light and the blue light
are mixed each other inside the sealing members 4, and become white
light. The white light passes through the protective cover 5
through the air layer 39, and is guided to the outside of the
light-emitting device 1. As a result, the light-emitting device 1
serves as a surface light source which emits white light. The white
light emitted by the light-emitting device 1 is used for
illuminating the inside of the room from the ceiling.
[0080] When the light-emitting devices 1 emit light, heat generated
by the light-emitting elements 3 is individually conducted to the
pads 9 on the substrate 2. The pads 9 functions as heat spreader
which spreads heat conducted from the light-emitting elements 3.
The heat which is spread by the pads 9 is mainly conducted from the
pads 9 to the protective cover 5, and radiated from the protective
cover 5 to the outside of the light-emitting devices 1. Therefore,
thermal transmission from the second surface 6b of the substrate 2
to the base 42 of the illumination device 41 is suppressed, and the
heat of the light-emitting elements 3 is not easily conducted to
the ceiling C.
[0081] In the first embodiment, the substrate 2 is formed of
synthetic resin material which has thermal conductance lower than
that of metal. In addition, the thermal insulating layer 44 is
interposed between the substrate 2 and the base 42. As a result,
thermal transmission from the substrate 2 to the base 42 is
suppressed, and thermal transmission from the substrate 2 to the
protective cover 5 is promoted. Therefore, the heat of the
light-emitting elements 3 can be positively radiated from the
protective cover 5.
[0082] According to the first embodiment, the pads 9, to which the
light-emitting elements 3 are affixed, project around the
light-emitting elements 3. In addition, the pads 9 have light
reflectance by virtue of presence of the silver plating layer 22.
Therefore, most of light going from the light-emitting elements 9
toward the substrate 2 is reflected by the silver plating layer 22,
and guided to a direction in which the light is to be taken out.
Thus, the light emitted by the light-emitting elements 3 can be
efficiently taken out of the light-emitting devices 1.
[0083] In addition, the depressions 36 of the protective cover 5
form the air layer 39 between the sealing members 4 covering the
light-emitting elements 3 and the protective cover 5. The light of
the light-emitting elements 3 which is transmitted through the
sealing members 4 is diffused when it passes through the interface
between the air layer 39 and the protective cover 5. The diffused
light is transmitted through the protective cover 5, and radiated
to the outside of the light-emitting device 1. Therefore, the
luminance of the surface of the protective cover 5 is made uniform,
and the light-emitting device 1 has good appearance while the
light-emitting device 1 is lit.
[0084] In addition, the light-emitting device 1 includes the
light-transmitting protective cover 5 which covers the substrate 2
and the light-emitting elements 3. Therefore, when the
light-emitting device 1 is used as light source of the illumination
device 41, it is possible to eliminate a shade and a globe from the
illumination device 41. This enables simplifying the structure of
the illumination device 41.
[0085] The substrate 2 to which the light-emitting elements 3 are
affixed is contained in the receptacle 35 of the protective cover
5, and affixed to the bottom surface 35a of the receptacle 35 by
the adhesive 38. The adhesive 38 is filled into the space between
the bottom surface 35a of the receptacle 35 and the substrate 2,
and surrounds the sealing members 4. This structure prevents dust
and water from infiltrating the space between the substrate 2 and
the protective cover 5. Therefore, the sealing members 4, through
which the light of the light-emitting elements 3 is transmitted,
are not easily soiled, and it is possible to add a waterproof
function to the illumination device 41.
[0086] In addition, the sealing members 4 are applied to the
substrate 2, to individually cover the forty-eight light-emitting
elements 3 and the bonding wires 28 and 29 which are connected to
the respective light-emitting elements 3. Therefore, it is possible
to reduce the quantity of the silicone resin and the fluorescent
material added to the silicone resin, in comparison with the case
where all the light-emitting elements 3 are continuously covered
with silicone resin. This is advantageous for suppressing the cost
of the light-emitting device 1.
[0087] On the other hand, the second conductor pattern 8, which
maintains all the pads 9 at the same potential when the pads 9 of
the first conductor pattern 7 are subjected to electroplating, is
formed of the common line 4 and a plurality of branch lines 25
which connect the common line 24 to the pads 9.
[0088] Therefore, electrical connection between the pads 9 achieved
by the second conductor pattern 8 can be severed by scraping off
the common line 24 by an electrical tool or the like. In addition,
since the common line 24 has a simple shape which extends in a
straight line along the long side 2b of the substrate 2, the common
line 24 can be scraped off by simply moving the electrical tool in
a straight line along the common line 24. Therefore, it is possible
to efficiently and easily perform work of removing the common line
24 from the substrate 2, and improve the productivity of the
light-emitting device 1.
[0089] In addition, the groove-like depressed part 33 which is left
after the common line 24 is scraped off is distant from the end
edge of the substrate 2, which defines the long side 2b of the
substrate 2, by the predetermined distance, and is positioned
between the end edge of the substrate 2 and the first power supply
patterns 15 on the substrate 2. As a result, the creepage distance
between the end edge of the substrate 2 and the first power supply
patterns 15 becomes longer than the clearance between the end edge
of the substrate 2 and the first power supply patterns 15, by a
length corresponding to the depth of the depressed part 33.
Therefore, when an electrical-conductive element is positioned
around the substrate 2, it is possible to secure an insulating
distance between the electrical-conductive element and the first
power supply patterns 15, and dielectric strength of the substrate
2 is improved.
Second Embodiment
[0090] FIG. 11 discloses an illumination device 51 according to a
second embodiment.
[0091] The illumination device 51 uses three light-emitting devices
1 as light source. The structure of the light-emitting device 1 is
the same as that of the first embodiment. In FIG. 11, a protective
cover is omitted to show the internal structure of the
light-emitting devices 1.
[0092] As illustrated in FIG. 11, the illumination device 51
includes a case 52 which is surface-mounted on the ceiling. The
case 52 is an example of a main body of the illumination device 51.
The case 52 has an elongated box shape, and has an elongated
opening part 53 which is opened downward. The three light-emitting
devices 1 and a power supply unit which lights the three
light-emitting devices 1 are contained in the case 52. The
light-emitting devices 1 are arranged in line along a longitudinal
direction of the case 52. The protective cover of each
light-emitting device 1 is exposed from the opening part 53 of the
case 52 to the outside of the case 52. In other words, the
protective cover of each light-emitting device 1 covers the opening
part 53 of the case 52 from the inside of the case 52. Therefore,
the case 52 does not need a dedicated translucent cover which
covers the opening part 53.
[0093] According to the second embodiment described above, it is
possible to provide the illumination device 51 which has the same
effect as that of the first embodiment.
Third Embodiment
[0094] FIG. 12 to FIG. 18 disclose a light-emitting device 61
according to a third embodiment.
[0095] The light-emitting device 61 which serves as illumination
light source comprises a substrate 62, a plurality of
light-emitting elements 63, and a pair of sealing members 64a and
64b. The substrate 62 is formed of a synthetic resin material such
as glass epoxy resin. The substrate 62 has an elongated shape which
has a pair of long sides 62a and 62b, and a pair of short sides 62c
and 62d. In addition, the substrate 62 has a first surface 65a, a
second surface 65b positioned opposite to the first surface 65a,
and an outer peripheral surface 65c which connects the first
surface 65a with the second surface 65b. The first and the second
surfaces 65a and 65b are flat surfaces. According to the second
embodiment, a length of the substrate 62 along the long sides 62a
and 62b is 230 mm, and a width of the substrate 62 along the short
sides 62c and 62d is 35 mm. In addition, a thickness of the
substrate 62 is preferably 0.5 mm to 1.8 mm. In the second
embodiment, the substrate 62 having a thickness of 1.0 mm is
used.
[0096] A plurality of piercing parts 66 are formed at end edges
which define the long sides 62a and 62b of the substrate 62. The
piercing parts 66 are arc-shaped cut-away portions which are opened
to the outer peripheral surface 63c of the substrate 62, and pierce
through the substrate 62 in a thickness direction. In addition, the
piercing parts 66 are arranged at intervals in the longitudinal
direction of the substrate 62.
[0097] A plurality of screws 68 are inserted through the respective
piercing parts 66. The screws 68 are an example of fixing parts
which fix the substrate 62 to a base of the illumination device,
and are screwed into the base through the piercing parts 66. In a
state where the screws 68 are screwed into the base, the end edge
of the substrate 62 is held between head parts of the screws 68 and
the base. Thereby, the substrate 62 is fixed to the base.
[0098] As illustrated in FIG. 13, a first conductor pattern 70 and
a second conductor pattern 71 are formed on the first surface 65a
of the substrate 62. The first conductor pattern 70 includes, for
example, nine pads 72, a positive power supply conductor 73, a
negative power supply conductor 74, and a relay conductor 75. The
pads 72 have a rectangular shape, and are arranged in line at
intervals in the longitudinal direction of the substrate 62.
[0099] Each pad 72 is divided into a first mounting area 76a and a
second mounting area 76b by a slit 72a. The slit 72a extends in the
center part of the pad 72 in a straight line in the longitudinal
direction of the substrate 62, and is opened to one end of the pad
72. Six depressed parts 77 are formed in the first mounting area
76a of each pad 72. The depressed parts 77 are opened to one side
edge of the pad 72, and arranged in line at intervals in the
longitudinal direction of the substrate 62. In the same manner, six
depressed parts 77 are formed in the second mounting area 76b of
each pad 72. The depressed parts 77 are opened to the slit 72a, and
arranged in line at intervals in the longitudinal direction of the
substrate 62.
[0100] As illustrated in FIG. 13, each of the pads 72 other than
one pad 72 positioned at the left end of the substrate 62 has a
pair of extension parts 79a and 79b. The extension parts 79a and
79b extend in straight line from one end of the pad 72 in the
longitudinal direction of the substrate 62, and are arranged in
parallel with each other at an interval. Each of the extension
parts 79a and 79b has six power supply terminals 80. The power
supply terminals 80 project from the extension parts 79a and 79b,
and are arranged in line at intervals in the longitudinal direction
of the substrate 62.
[0101] One extension part 79a of each pad 72 extends along one side
edge of the adjacent pad 72. The power supply terminals 80 of the
extension part 79a are inserted into the respective depressed parts
77 opened to one side edge of the pad 72. The extension part 79a
and the side edge of the pad 72 are electrically separated by
providing an insulating space between them. In the same manner, the
power supply terminals 80 of the extension part 79a and the
depressed parts 77 are electrically separated by providing
insulating spaces between them.
[0102] The other extension part 79b of each pad 72 is inserted into
the slit 72a of the adjacent pad 72. The power supply terminals 80
of the extension part 79b are inserted into the respective
depressed parts 77 opened to the slit 72a. The extension part 79b
and the pad 72 are electrically separated by providing an
insulating space positioned inside the slit 72a. In the same
manner, the power supply terminals 80 of the extension part 79b and
the depressed parts 77 are electrically separated by providing
insulating spaces between them.
[0103] Therefore, as is clear from FIG. 13, the pads 72 are
arranged in line in the longitudinal direction of the substrate 62,
in a state where the extension parts 79a and 79b are alternately
reversed in the width direction of the substrate 62.
[0104] As illustrated in FIG. 13, the positive power supply
conductor 73 extends over the whole length of the substrate 62 to
run along the long side 62b of the substrate 62. The negative power
supply conductor 74 extends along the longitudinal direction of the
substrate 62 to run along the long side 62b of the substrate 62.
The left end of the negative power supply conductor 74 is connected
to the pad 72 positioned at the left end of the substrate 62.
[0105] The positive power supply conductor 73 has an anode terminal
81. In the same manner, the negative power supply conductor 74 has
a cathode terminal 82. The anode terminal 81 and the cathode
terminal 82 are aligned at an interval in the left end part of the
substrate 62.
[0106] The relay conductor 75 extends along the longitudinal
direction of the substrate 62 to run along the long side 62b of the
substrate 62. The relay conductor 75 is positioned in a right end
part of the substrate 62. The relay conductor 75 includes a pair of
power supply patterns 84a and 84b. The power supply patterns 84a
and 84b extend in a straight line in the longitudinal direction of
the substrate 62, and are arranged in parallel with each other with
a space between them. Each of the power supply patterns 84a and 84b
has six power supply terminals 85. The power supply terminals 85
project from the power supply patterns 84a and 84b, and are
arranged in line at intervals in the longitudinal direction of the
substrate 62.
[0107] One power supply pattern 84a extends along one side edge of
the pad 72 positioned at the right end of the substrate 62. The
power supply terminals 85 of the power supply pattern 84a are
inserted into the respective depressed parts 77 opened to the side
edge of the pad 72. The power supply pattern 84a and the side edge
of the pad 72 are electrically separated by providing an insulating
space between them. In the same manner, the power supply terminals
85 of the power supply pattern 84a and the depressed parts 77 of
the pad 72 are electrically separated by providing insulating
spaces between them.
[0108] The other power supply pattern 84b is inserted into the slit
72a of the pad 72 positioned at the right end of the substrate 62.
The power supply terminals 85 of the power supply pattern 84b are
inserted into the respective depressed parts 77 opened to the slit
72a. The power supply pattern 84b and the pad 72 are electrically
separated by providing an insulating space between them. In the
same manner, the power supply terminals 85 of the power supply
pattern 84b and the depressed parts 77 of the pad 72 are
electrically separated by providing insulating spaces between
them.
[0109] As illustrated in FIG. 12 and FIG. 13, a power supply
connector 86 is soldered to the anode terminal 81 and the cathode
terminal 82. The power supply connector 86 is positioned on the
first surface 65a of the substrate 62, and electrically connected
to the power supply circuit through lead lines 86a. In addition,
the negative power supply conductor 74 and the relay conductor 85
are short-circuited through a relay connector 87.
[0110] As illustrated in FIG. 17, the first conductor pattern 70
including the pads 72 has a three-layer structure including a
copper layer 88, a nickel plating layer 89, and a silver plating
layer 90. The copper layer 88 is formed by etching a copper foil
deposited on the first surface 65a of the substrate 62. The nickel
plating layer 89 is formed on the copper layer 88 by subjecting the
copper layer 88 to electroplating. The silver plating layer 90 is
formed on the nickel plating layer 89 by subjecting the nickel
plating layer 89 to electroplating. The silver plating layer 90
covers the nickel plating layer 89, and forms a reflecting layer
which is exposed to the surface of the first conductor pattern 70.
Therefore, the surface of the first conductor pattern 70 is a
light-reflecting surface.
[0111] The nickel plating layer 89 preferably has a thickness of 5
.mu.m or more. In the same manner, the silver plating layer 90
preferably has a thickness of 1 .mu.m or more. Specifying the
thicknesses of the nickel plating layer 89 and the silver plating
layer 90 like this solves the problem of variations in thicknesses
of the nickel plating layer 89 and the silver plating layer 90, and
makes the light reflectance of all the pads 72 uniform.
[0112] The second conductor pattern 71 is used for maintaining all
the pads 72 at the same potential when the pads 72 of the first
conductor pattern 70 to electroplating. Specifically, the second
conductor pattern 71 includes a common line 92 and a plurality of
branch lines 93 as illustrated in FIG. 13. The common line 92
extends in a straight line over the whole length of the substrate
62 to run along the long side 62a of the substrate 62.
Simultaneously, the common line 92 is distant from the end edge of
the substrate 62, which defines the long side 62a of the substrate
62, by a predetermined distance D.
[0113] In addition, the common line 92 has a plurality of curved
parts 94 in positions corresponding to the piercing parts 66 of the
substrate 62. The curved parts 94 are curved in arc shape in a
direction going away from the edges of the piercing parts 66. By
presence of the curved parts 94, the common line 92 is distant from
the edges of the piercing parts 66, by at least the same distance
as the distance D in the parts corresponding to the piercing parts
66.
[0114] The branch lines 93 are branched from the common line 92,
and extend in a straight line toward the pads 72. The branch lines
93 are arranged at intervals in the longitudinal direction of the
substrate 62. Distal ends of the branch lines 93 are electrically
connected to all the pads 72 and the power supply pattern 84a of
the relay conductor 75. In other words, all the pads 72 and the
relay conductor 75 are electrically connected to the common line 92
through the branch lines 93.
[0115] The second conductor pattern 71 is formed on the first
surface 65a of the substrate 62 simultaneously with the first
conductor pattern 70, and has the same three-layer structure as
that of the first conductor pattern 70. Therefore, the surface of
the second conductor pattern 71 is formed of a silver plating
layer, and has light reflectance.
[0116] Each light-emitting element 63 is a light-emitting diode
chip as in the first embodiment, and has a positive electrode and a
negative electrode. The light-emitting elements 63 are affixed to
the first mounting areas 76a and the second mounting areas 76b of
the pads 72 by a silicone-resin-based adhesive 96. Specifically,
six light-emitting elements 63 are arranged in the first mounting
area 76a of each pad 72 in line at intervals in the longitudinal
direction of the substrate 62, and six light-emitting elements 63
are arranged in the second mounting area 76b of each pad 72 in line
at intervals in the longitudinal direction of the substrate 62.
Therefore, each pad 72 includes twelve light-emitting elements 63.
The light-emitting elements 63 on each pad 72 form two rows of
light-emitting elements which are successively arranged in the
longitudinal direction of the substrate 62.
[0117] As illustrated in FIG. 14 and FIG. 17, the positive
electrode of each light-emitting element 63 is electrically
connected to the pad 72, to which the light-emitting element 63 is
affixed, by a bonding wire 98. The negative electrode of each
light-emitting element 63 is electrically connected to the power
supply terminals 80 of the adjacent pad 72 and the power supply
terminals 85 of the power supply patterns 84a and 84b by another
bonding wire 99. Specifically, as illustrated in FIG. 18, the
light-emitting device 61 has nine parallel circuits 100a, 100b,
100c, 100d, 100e, 100f, 100g, 100h, and 100i, in each of which
twelve light-emitting elements 63 are connected in parallel. In
addition, the nine parallel circuits 100a, 100b, 100c, 100d, 100e,
100f, 100g, 100h, and 100i are connected in series.
[0118] In addition, in the third embodiment, to prevent malfunction
of the light-emitting device 61, capacitor 101 is connected to each
of the nine parallel circuits 100a, 100b, 100c, 100d, 100e, 100f,
100g, 100h, and 100i. Simultaneously, a capacitor 101 is also
connected to a circuit which connects the parallel circuits 100a,
100b, 100c, 100d, 100e, 100f, 100g, 100h, and 100i in series. The
capacitors 101 are mounted on the first surface 65a of the
substrate 62.
[0119] In the third embodiment, the power supply terminals 80 and
85 to which the bonding wire 99 is connected are inserted into the
depressed parts 77 of the adjacent pad 72. In other words, since
the power supply terminals 80 and 85 go toward the center parts of
the first and the second mounting areas 76a and 76b, the
light-emitting elements 63 can be affixed to the center parts of
the first and the second mounting areas 76a and 76b, without
changing the lengths of the bonding wires 98 and 99. Therefore, it
is possible to conduct the heat generated by the light-emitting
elements 63 to a wide range of the first and the second mounting
areas 76a and 76b, and efficiently radiate the heat from the pads
72.
[0120] The second conductor pattern 71 which all the pads 72 at the
same potential becomes redundant after the first conductor pattern
70 is subjected to electroplating. Therefore, in the third
embodiment, after the first conductor pattern 70 is subjected to
electroplating, the common line 92 of the second conductor pattern
71 is removed, to sever electrical connection between the pads 72
obtained by the second conductor pattern 71.
[0121] As illustrated in FIG. 14, FIG. 15 and FIG. 17, a depressed
part 105 is formed in the first surface 65a of the substrate 62.
The depressed part 105 is a trace which is left after the common
line 92 is removed, and extends along the long side 62a of the
substrate 62. The depressed part 105 is a groove which is defined
by a bottom surface 105a and a pair of side surfaces 105b and 105c,
and opened to the first surface 65a of the substrate 62.
[0122] In addition, the depressed part 105 has a plurality of
curved parts 106 in positions corresponding to the piercing parts
66 of the substrate 62. The curved parts 106 are formed in a shape
which agrees with the shape of the curved parts 94 of the common
line 92, to detour around the piercing parts 66. The depressed part
105 having the above structure is positioned between the end edge
of the substrate 62, which defines the long side 62a of the
substrate 62, and the pads 72, and distant from the end edge of the
substrate 62 by a predetermined distance. According to the third
embodiment, the depressed part 105 has a width of 1 mm, and a depth
of 0.3 mm.
[0123] By presence of the depressed part 105 as described above,
only the branch lines 93 of the second conductor pattern 71 remain
on the first surface 65a of the substrate 62. The remaining branch
patterns 93 are electrically separated. In addition, a creepage
distance between the end edge of the substrate 62 which defines the
long side 62a of the substrate 62 and the pads 72 is a value
obtained by adding the height of the side surfaces 105b and 105c of
the depressed part 105. Therefore, the creepage distance is longer
than the clearance between the end edge of the substrate 62 and the
pads 72 by the depth of the depressed part 105. The shape of the
depressed part 105 is not limited to the third embodiment. For
example, the depressed part 105 may have a V-shaped or U-shaped
cross section in the direction perpendicular to the longitudinal
direction of the substrate 62.
[0124] The sealing members 64a and 64b are elements for sealing the
light-emitting elements 63, which are arranged in two lines, and
the bonding wires 98 and 99 on the pads 72. The sealing members 64a
and 64b are formed of transparent silicone resin, in which
fluorescent material is mixed, and extend in a straight line along
the longitudinal direction of the substrate 62.
[0125] As illustrated in FIG. 12 and FIG. 17, the first surface 65a
of the substrate 62 is covered with a white resist layer 108,
except for areas on which parts such as the light-emitting elements
63 and the capacitors 101 are mounted. The resist layer 108 has
light reflectance. The resist layer 108 continuously covers the
first conductor pattern 70, the branch lines 93, and the depressed
part 105. Therefore, the first conductor pattern 70, the branch
lines 93 and the depressed part 105 on the first surface 65a of the
substrate 62 are not easily viewed.
[0126] As illustrated in FIG. 16 and FIG. 17, eighteen rectangular
thermally radiative sheets 110 are deposited on the second surface
65b of the substrate 62. The thermally radiative sheets 110 are an
example of conductors, and are formed of a copper foil which has
excellent heat conductance. The thermally radiative sheets 110 are
arranged in two lines at intervals in the longitudinal direction of
the substrate 62, to correspond to the pads 72 of the first surface
65a. The adjacent thermally radiative sheets 110 are thermally
separated by a plurality of first slits 111, which extend in the
longitudinal direction of the substrate 62, and a plurality of
second slits 112 which extend in the direction perpendicular to the
longitudinal direction of the substrate 62. In addition, the
thermally radiative sheets 110 and the second surface 65b of the
substrate 62 is covered with a resist layer 113.
[0127] By depositing the thermally radiative sheets 110 on the
second surface 65b of the substrate 62, it is possible to equalize
temperature distribution of the substrate 62 which receives the
heat of the light-emitting elements 63. Therefore, the thermal
radiation property of the substrate 62 can be improved. In
particular, by providing the second slits 112, which run along the
direction perpendicular to the longitudinal direction of the
substrate 62, between the adjacent thermally radiative sheets 110,
it is possible to suppress a warp and deformation of the substrate
62 due to heat.
[0128] Next, a process of manufacturing the light-emitting device
61 will be explained hereinafter with reference to FIG. 13 to FIG.
15.
[0129] First, the first conductor pattern 70 and the second
conductor pattern 71 are formed on the first surface 65a of the
substrate 62. Specifically, the copper foil deposited on the first
surface 65a is etched, and thereby copper layers 88 of the first
and the second conductor pattern 70 and 71 are formed. Among the
copper layer 88 of the first conductor pattern 70, parts which form
the pads 72 are electrically connected to each other through the
copper layer 88 of the second conductor pattern 71. Therefore, all
the parts of the copper layer 88 of the first conductor pattern 70,
which form the pads 72, are maintained at the same potential.
[0130] In this state, the copper layer 88 of the first conductor
pattern 70 is subjected to electroplating, and thereby a nickel
plating layer 89 is formed on the copper layer 88. Thereafter, the
nickel plating layer 89 is subjected to electroplating, and thereby
a silver plating layer 90 is formed on the nickel plating layer 89.
In the step of performing electroplating, all the parts which form
the pads 72 in the copper layer 88 of the first conductor pattern
70 are maintained at the same potential. Therefore, the nickel
plating layer 89 and the silver plating layer 90 are formed on the
copper layer 88 of the first conductor pattern 70, by using the
copper layer 88 of the first conductor pattern 70 as cathode, using
the same metal as plating layer as anode, and causing an electric
current to flow between the cathode and the anode. The nickel
plating layer 89 and the silver plating layer 90 are also formed on
the copper layer 88 of the second conductor pattern 71
simultaneously with the first conductor pattern 70.
[0131] Thereafter, as illustrated in FIG. 14, the common line 92 of
the second conductor pattern 71 is removed from the first surface
65a of the substrate 62. Specifically, the common line 92 on the
first surface 65a is scraped away in the same manner as the first
embodiment. As a result, electrical connection between the pads 72
of the first conductor pattern 70 and the second conductor pattern
71 is severed, and the pads 72 are maintained in a state of being
electrically independent.
[0132] Simultaneously with scraping away the common line 92 from
the first surface 65a, a groove-like depressed part 105 is formed
in the first surface 65a. The depressed part 105 has the curved
parts 106, which are curved to detour around the piercing parts 66,
in positions corresponding to the piercing parts 66 of the
substrate 62.
[0133] The depressed part 105 crosses over the bases of the branch
lines 93 branching off from the common line 92. As a result, the
branch lines 93 are left on the first surface 65a of the substrate
62, in a state of being electrically separated from each other.
[0134] Thereafter, six light-emitting elements 63 are affixed on
each of the first and the second mounting areas 76a and 76b of each
pad 72. Then, the positive electrodes of the light-emitting
elements 63 are electrically connected to the pads 72, to which the
light-emitting elements 63 are affixed, by bonding wires 98. In the
same manner, the negative electrodes of the light-emitting elements
63 are connected to the power supply terminals 80 of the adjacent
pads 72 and the power supply terminals 85 of the power supply
patterns 84a and 84b by bonding wires 99.
[0135] Then, the light-emitting elements 63 arranged in two lines
and the bonding wires 98 and 99 are sealed on the pads 72 by the
sealing members 64a and 64b. Thereby, the light-emitting device 61
as illustrated in FIG. 15 is formed.
[0136] According to the third embodiment having the above
structure, the second conductor pattern 71 which maintains the pads
72 of the first conductor pattern 70 at the same potential is
formed of the common line 92 and the branch lines 93 which are
branched off from the common line 92 and reach the pads 72.
Therefore, electrical connection between the pads 72 obtained by
the second conductor pattern 71 can be severed, by removing the
common line 92 from the substrate 62.
[0137] Therefore, in the same manner as the first embodiment, it is
possible to efficiently and easily perform the work of cutting off
electrical connection between the pads 72, and improve the
productivity of the light-emitting device 61.
[0138] In addition, the depressed part 105 which is left after the
common line 92 is scraped away is distant from the end edge of the
substrate 62 by the predetermined distance, and positioned between
the end edge of the substrate 62 and the pads 72. As a result, the
creepage distance between the end edge of the substrate 62 and the
pads 72 becomes longer than the clearance between the end edge of
the substrate 62 and the pads 72, by a length corresponding to the
depth of the depressed part 105, and it is possible to secure an
insulating distance between the end edge of the substrate 62 and
the pads 72.
[0139] In addition, according to the third embodiment, the
depressed part 105 has the curved parts 106, which are curved to
detour around the piercing parts 66, in positions corresponding to
the piercing parts 66 of the substrate 62. Therefore, it is
possible to equally secure insulating distances from the edges of
the piercing parts 66 to the curved parts 106, and increase the
dielectric strength of the substrate 62. Thus, even when the screws
68 inserted through the piercing parts 66 are formed of metal,
insulation of the screws 68 from the pads 72 can be sufficiently
secured, and the reliability of electrical insulation of the
light-emitting device 61 can be improved.
Fourth Embodiment
[0140] FIG. 19 discloses a fourth embodiment.
[0141] The fourth embodiment is different from the third
embodiment, in that a plurality of through-holes 120 are provided
in outer edge parts of a substrate 62 running along long sides 62a
and 62b. The other parts of the structure of a light-emitting
device 61 are the same as those of the third embodiment.
[0142] The through-holes 120 of the substrate 62 are used for
inserting screws which fix the substrate 62 to a base of an
illumination device. The through-holes 120 are arranged at
intervals in a longitudinal direction of the substrate 62. In
addition, a depressed part 105 on a first surface 65a of the
substrate 62 has a plurality of curved parts 106 in positions
corresponding to the through-holes 120. The curved parts 106 are
curved in an arc shape in a direction going away from the end edge
of the substrate 62, to detour around the through-holes 120.
[0143] Also in the fourth embodiment as described above, an
insulating distance from the through-holes 120 to the depressed
part 105 can be secured, by presence of the curved parts 106.
Therefore, the dielectric strength of the substrate 62 is improved
and it is possible to sufficiently secure insulation of the screws
from pads 72, even when the screws inserted through the
through-holes 120 are formed of metal.
Fifth Embodiment
[0144] FIG. 20 to FIG. 24 disclose a fifth embodiment.
[0145] The fifth embodiment is different from the third embodiment,
mainly in the shape of the second conductor pattern and the
structure for cutting off electrical connection between pads
obtained by the second conductor pattern. The basic structure of
the substrate of the fifth embodiment other than these points is
the same as that of the third embodiment. Therefore, in the fifth
embodiment, constituent elements which are the same as those in the
third embodiment are denoted by the same respective reference
numerals as those of the third embodiment, and explanation thereof
is omitted.
[0146] As illustrated in FIG. 20, a first conductor pattern 70
formed on a first surface 65a of a substrate 62 includes fourteen
pads 72. The pads 72 are arranged in line at intervals in a
longitudinal direction of the substrate 62.
[0147] The fourteen pads 72 are electrically connected by a second
conductor pattern 200 and maintained at the same potential, before
the pads 72 are subjected to electroplating. The second conductor
pattern 200 is formed on the first surface 65a of the substrate 62.
The second conductor pattern 200 has a relay line 201, and a
plurality of connection lines 202. As illustrated in FIG. 20 and
FIG. 22, the relay line 201 is positioned at the left end of the
substrate 62, and extends along a short side 62c of the substrate
62. The relay line 201 electrically connects the pad 72 located at
the left end of the substrate 62 with the first conductor pattern
70.
[0148] The connection lines 202 are drawn from the pads 72 and a
power supply pattern 84a positioned at the right end of the
substrate 62, and arranged between the pads 72 and a long side 62a
of the substrate 62. End parts of each connection line 202 located
at the end reverse to the pad 72 is guided toward the long side 62a
of the substrate 62. According to the fifth embodiment, the end
parts of the connection lines 202 are assigned to removal positions
P1, P2, P3 and P4 which are set in four positions of the long side
62a of the substrate 62. The removal positions P1, P2, P3 and P4
are arranged at intervals in the longitudinal direction of the
substrate 62.
[0149] Specifically, as illustrated in FIG. 20 and FIG. 22, the end
parts of the four connection lines 202 which correspond to the
first pad 72, located at the left end of the substrate 62, to the
fourth pad 72 are guided to removal position P1 and collected
therein. The end parts of the four connection lines 202 which
correspond to the fifth pad 72 to the eighth pad 72 are guided to
removal position P2 and collected therein. The end parts of the
four connection lines 202 which correspond to the ninth pad 72 to
the twelfth pad 72 are guided to removal position P3 and collected
therein. The end parts of the two connection lines 202 which
correspond to the thirteenth pad 72 to the fourteenth pad 72, and
the end part of the connection line 202 which corresponds to the
power supply pattern 84a are guided to removal position P4 and
collected therein. The end parts of the connection lines 202 guided
to each of the removal positions P1, P2, P3 and P4 are electrically
connected to each other.
[0150] In addition, in the fifth embodiment, a thermally radiative
sheet 203 is deposited on a second surface 65b of the substrate 62.
The thermally radiative sheet 203 is an example of a conductor, and
formed of metal material which has excellent heat conductance such
as copper foil. The thermally radiative sheet 203 covers the whole
of the second surface 65b of the substrate 62.
[0151] The second conductor pattern 200 becomes redundant after the
pads 72 are subjected to electroplating. Therefore, in the fifth
embodiment, after the pads 72 are subjected to electroplating,
electrical connection between the pads 72 obtained by the second
conductor pattern 200 is severed.
[0152] Specifically, part of the short side 62c of the substrate 62
and the removal positions P1, P2, P3 and P4 of the long side 62a of
the substrate 62 are scraped away, and thereby the relay line 201
is severed, and the end parts of the connection lines 202 are
removed. Therefore, a depressed part 204 which is traces of
scraping away the parts of the substrate 62 is formed in the
substrate 62. The depressed part 204 includes first to fifth cutoff
parts 204a, 204b, 204c, 204d, and 204e. The first cutoff part 204a
is formed in the short side 62c of the substrate 62. The second to
fifth cutoff parts 204b, 204c, 204d, and 204e are formed in four
positions of the long side 62a of the substrate 62.
[0153] Each of the first to fifth cutoff parts 204a, 204b, 204c,
204d, and 204e has a bottom surface 205a and an internal periphery
surface 205b, and is opened to the first surface 65a and the outer
peripheral surface 65c of the substrate 62. The bottom surface 205a
connects to the outer peripheral surface 65c of the substrate 62.
Therefore, the first to fifth cutoff parts 204a, 204b, 204c, 204d,
and 204e do not pierce through the substrate 62 in the thickness
direction, and are positioned in corner parts defined by the first
surface 65a and the outer peripheral surface 65c of the substrate
62.
[0154] By presence of the first to fifth cutoff parts 204a, 204b,
204c, 204d, and 204e as described above, the pads 72 are
electrically separated from one another, although most of the relay
line 201 and the connection lines 202 are left on the first surface
65a of the substrate 62. In addition, as illustrated in FIG. 24, a
creepage distance between the first conductor pattern 70 on the
first surface 65a of the substrate 62 and the thermally radiative
sheet 203 deposited on the second surface 65b of the substrate 62
is a value, which is obtained by adding the length of the bottom
surface 204a of the depressed part 204. Therefore, the creepage
distance is longer than clearance between the first conductor
pattern 70 on the first surface 65a of the substrate 62 and the
thermally radiative sheet 203 deposited on the second surface 65b
by the length of the bottom surface 204a of the recessed part 204.
As a result, an insulation distance between the first conductor
pattern 70 and the thermally radiative sheet 203 can be
sufficiently secured, and the dielectric strength of the substrate
62 is improved.
[0155] In the fifth embodiment, three through-holes 206 are formed
in the center part of the substrate 62. The through-holes 206 are
used for inserting screws, which fix the substrate 62 to a base of
an illumination device, and arranged at intervals in the
longitudinal direction of the substrate 62.
[0156] According to the fifth embodiment as described above,
electrical connection between all the pads 72 can be removed, by
scraping away the four parts of the long side 62a of the substrate
62 and a part of the short side 62c of the substrate 62. Therefore,
the range of the part which is scraped away from the substrate 62
is remarkably reduced, in comparison with the first embodiment and
the third embodiment. As a result, the work of removing the second
conductor pattern 71 can be easily performed in a short time, and
the manufacturing cost of the substrate 62 can be reduced.
[0157] Simultaneously, since the range of the part which is scraped
away from the substrate 62 is reduced, the quantity of grinding
swarf which is generated when the substrate 62 is scraped is
reduced. This reduces the possibility that grinding swarf adheres
to the pads 72, and prevents deterioration in the workability when
the light-emitting elements are affixed to the pads 72.
[0158] In the light-emitting devices of the first and the third
embodiments, the light-emitting diode chips are mounted on the pads
by the chip-on-board method. However, a light-emitting diode
package obtained by combining a plurality of light-emitting diode
chips may be mounted on the pads by the surface-mount method.
[0159] Although the pads are preferably used as a power supply
wiring pattern, they are not limited to use as wiring pattern.
Specifically, when a reflecting layer is formed on the pads, the
electrical-conduction function of the pads is not indispensable,
and there are cases where the pads have only to exhibit a function
of reflecting light emitted by the light-emitting elements, or a
function as heat spreader which spreads heat generated by the
light-emitting elements.
[0160] In addition, it is not indispensable that the sealing
members contain fluorescent material. For example, the red light,
green light, or blue light emitted by the light-emitting elements
may be directly radiated to the outside of the light-emitting
device.
[0161] The illumination device using the light-emitting devices is
applicable to light-source devices of an electric light bulb type,
illumination tools used indoors or outdoors such as spotlights, and
displays.
[0162] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *